High Levels of Exercise May Be OK for Middle-Aged Hearts

Contrary to some concerns, midlife endurance exercise may be good for the heart.

Posted Feb 08, 2019

Most middle-aged men who participate in high levels of vigorous aerobic exercise every week are not damaging their hearts or increasing mortality risk, according to recent findings of a decades-long study. This paper, “Association of All-Cause and Cardiovascular Mortality With High Levels of Physical Activity and Concurrent Coronary Artery Calcification,” was published online January 30 in JAMA Cardiology.

Courtesy of Kiehl's Since 1851
Christopher Bergland running 135-miles nonstop through Death Valley in July.
Source: Courtesy of Kiehl's Since 1851

Previous research has raised questions about whether or not extreme amounts of aerobic exercise or doing “too much” physical activity might be harmful to the heart. More specifically, the concern among cardiologists has been that athletes who perform high levels of cardiovascular exercise often have higher-than-average levels of coronary artery calcification (CAC). 

The primary goal of the recent study (DeFina et al., 2019) was to identify if the presence of high levels of CAC among middle-aged men who performed so-called “extreme” levels of weekly physical activity is correlated with an increased risk of early death.

“Extreme exercise was defined as eight or more hours a week of activity at an average of 10 metabolic equivalents, or METs,” senior author Benjamin Levine of the University of Texas Southwestern Medical Center said in a statement. MET-Minutes are a standard measure of energy exerted during physical activity and can be monitored easily on most indoor cardio machines.

Levine is also director of the Institute for Exercise and Environmental Medicine (IEEM), which is a collaboration between UTSWMed and Texas Health Presbyterian Hospital Dallas. 

Here's a short YouTube video describing this research:

The cohort for this study consisted of 21,758 generally healthy men (ages 40 to 80) who were observed between 1998 and 2014. Over the course of this study, participants self-reported their activity levels and underwent periodic coronary calcium scanning. Most of the participants in this study were runners—but the cohort also included swimmers, cyclists, triathletes, and rowers. 

Notably, this study did not include women. According to the researchers, women have much lower rates of death during middle age, which made a valid statistical comparison between middle-aged male and female “extreme” athletes impossible. Levine noted: "The trend seems to be similar in men and women, but we can't say anything convincingly because the death rates were so low in women." 

"Being a high-level athlete was clearly protective and not injurious for those with lower levels of arterial plaques. In fact, middle-aged men who didn't already have hardening of the arteries saw their odds for early death fall by half if they regularly engaged in vigorous activity. Particularly the male athletes tended to have more coronary plaques, and the plaques they did have were virtually all calcified,” Levine said. “But no study had ever taken the next logical step. No one actually ever determined whether that made them at higher risk of death or not, and that's really the whole question. Who cares if they have more calcium if they don't die [prematurely]?”

Photo by Christopher Bergland
Source: Photo by Christopher Bergland

As a fanatical ultra-marathon runner and extreme-distance triathlete, I pushed my body to the outer limits of physical endurance throughout my 20s and 30s. When I was 38, I retired from ultra-running after I almost accidentally killed myself while breaking a Guinness World Record by running 153.76 miles on a treadmill in 24 hours. Under those conditions, my heart actually started to eat itself and my kidneys almost shut down. After spending four days in the ICU, I decided to retire from what I considered “extreme” endurance exercise at the time. (Yes, I was a freak!) Hopefully this story can serve as a cautionary tale for other ultra-endurance athletes with an "extreme" mindset about the importance of avoiding the temptation to push yourself ridiculously hard once you're past your prime.

For any wonky science readers out there, this is how I describe the nitty-gritty, lab-report details from this ICU experience in The Athlete’s Way:

"I was catheterized and on the verge of kidney failure with CPK levels of 176,700 “international units” per liter (normal is 24 to 195IU/L). CPK is a byproduct of muscle breakdown and is a gloppy and viscous fluid that blocks the filtering screens of the kidneys. My CK-MB, an enzyme that measures heart muscle breakdown with a normal range of 0 to 34.4 ng/ml was at 770 “nanograms” per milliliter. The saddest lesson I learned from the post-Guinness World Record blood work was that, in an attempt to squeeze every ounce of passion from my body, my heart had begun to eat itself. My intense desire to suck the marrow out of life through ultra-endurance sports would eventually cause me to self-destruct. I made a vow in the ICU that I would never push my body to the limit again.”

Reading the latest DeFina et al. (2019) study caused me to let out an audible sigh of relief. As a 53-year-old, I’m a much slower runner now, but I still fit the demographic of their study. Most days of the week, I jog for about 90 minutes and do high-intensity interval training (HIIT) a couple times a week. Even though I feel great and don’t have any aches or pains in my joints, a little voice in my head has often wondered if continuing to perform high levels of physical activity as a middle-aged person might be bad for my heart. I'm glad to learn that it seems to be A-OK for me to keep doing what I'm doing. 

That said, I’m going to keep listening to my body and not recklessly “over do it” in a way that puts too much strain on any part of my body, including my heart. If you're middle-aged, I'd recommend you do the same.

As always: Please use common sense and consult with your primary care physician before beginning any new exercise regimen.

References

Laura F. DeFina, Nina B. Radford, Carolyn E. Barlow, Benjamin L. Willis, David Leonard, William L. Haskell, Stephen W. Farrell, Andjelka Pavlovic, Katelyn Abel, Jarett D. Berry, Amit Khera, Benjamin D. Levine. "Association of All-Cause and Cardiovascular Mortality With High Levels of Physical Activity and Concurrent Coronary Artery Calcification." JAMA Cardiology (First published online: January 30, 2019) DOI: 10.1001/jamacardio.2018.4628

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